var inherits = require('util').inherits

module.exports = function (Buffer, Hash) {
  var K = [
    0x428a2f98, 0xd728ae22, 0x71374491, 0x23ef65cd,
    0xb5c0fbcf, 0xec4d3b2f, 0xe9b5dba5, 0x8189dbbc,
    0x3956c25b, 0xf348b538, 0x59f111f1, 0xb605d019,
    0x923f82a4, 0xaf194f9b, 0xab1c5ed5, 0xda6d8118,
    0xd807aa98, 0xa3030242, 0x12835b01, 0x45706fbe,
    0x243185be, 0x4ee4b28c, 0x550c7dc3, 0xd5ffb4e2,
    0x72be5d74, 0xf27b896f, 0x80deb1fe, 0x3b1696b1,
    0x9bdc06a7, 0x25c71235, 0xc19bf174, 0xcf692694,
    0xe49b69c1, 0x9ef14ad2, 0xefbe4786, 0x384f25e3,
    0x0fc19dc6, 0x8b8cd5b5, 0x240ca1cc, 0x77ac9c65,
    0x2de92c6f, 0x592b0275, 0x4a7484aa, 0x6ea6e483,
    0x5cb0a9dc, 0xbd41fbd4, 0x76f988da, 0x831153b5,
    0x983e5152, 0xee66dfab, 0xa831c66d, 0x2db43210,
    0xb00327c8, 0x98fb213f, 0xbf597fc7, 0xbeef0ee4,
    0xc6e00bf3, 0x3da88fc2, 0xd5a79147, 0x930aa725,
    0x06ca6351, 0xe003826f, 0x14292967, 0x0a0e6e70,
    0x27b70a85, 0x46d22ffc, 0x2e1b2138, 0x5c26c926,
    0x4d2c6dfc, 0x5ac42aed, 0x53380d13, 0x9d95b3df,
    0x650a7354, 0x8baf63de, 0x766a0abb, 0x3c77b2a8,
    0x81c2c92e, 0x47edaee6, 0x92722c85, 0x1482353b,
    0xa2bfe8a1, 0x4cf10364, 0xa81a664b, 0xbc423001,
    0xc24b8b70, 0xd0f89791, 0xc76c51a3, 0x0654be30,
    0xd192e819, 0xd6ef5218, 0xd6990624, 0x5565a910,
    0xf40e3585, 0x5771202a, 0x106aa070, 0x32bbd1b8,
    0x19a4c116, 0xb8d2d0c8, 0x1e376c08, 0x5141ab53,
    0x2748774c, 0xdf8eeb99, 0x34b0bcb5, 0xe19b48a8,
    0x391c0cb3, 0xc5c95a63, 0x4ed8aa4a, 0xe3418acb,
    0x5b9cca4f, 0x7763e373, 0x682e6ff3, 0xd6b2b8a3,
    0x748f82ee, 0x5defb2fc, 0x78a5636f, 0x43172f60,
    0x84c87814, 0xa1f0ab72, 0x8cc70208, 0x1a6439ec,
    0x90befffa, 0x23631e28, 0xa4506ceb, 0xde82bde9,
    0xbef9a3f7, 0xb2c67915, 0xc67178f2, 0xe372532b,
    0xca273ece, 0xea26619c, 0xd186b8c7, 0x21c0c207,
    0xeada7dd6, 0xcde0eb1e, 0xf57d4f7f, 0xee6ed178,
    0x06f067aa, 0x72176fba, 0x0a637dc5, 0xa2c898a6,
    0x113f9804, 0xbef90dae, 0x1b710b35, 0x131c471b,
    0x28db77f5, 0x23047d84, 0x32caab7b, 0x40c72493,
    0x3c9ebe0a, 0x15c9bebc, 0x431d67c4, 0x9c100d4c,
    0x4cc5d4be, 0xcb3e42b6, 0x597f299c, 0xfc657e2a,
    0x5fcb6fab, 0x3ad6faec, 0x6c44198c, 0x4a475817
  ]

  var W = new Array(160)

  function Sha512() {
    this.init()
    this._w = W

    Hash.call(this, 128, 112)
  }

  inherits(Sha512, Hash)

  Sha512.prototype.init = function () {

    this._a = 0x6a09e667|0
    this._b = 0xbb67ae85|0
    this._c = 0x3c6ef372|0
    this._d = 0xa54ff53a|0
    this._e = 0x510e527f|0
    this._f = 0x9b05688c|0
    this._g = 0x1f83d9ab|0
    this._h = 0x5be0cd19|0

    this._al = 0xf3bcc908|0
    this._bl = 0x84caa73b|0
    this._cl = 0xfe94f82b|0
    this._dl = 0x5f1d36f1|0
    this._el = 0xade682d1|0
    this._fl = 0x2b3e6c1f|0
    this._gl = 0xfb41bd6b|0
    this._hl = 0x137e2179|0

    this._len = this._s = 0

    return this
  }

  function S (X, Xl, n) {
    return (X >>> n) | (Xl << (32 - n))
  }

  function Ch (x, y, z) {
    return ((x & y) ^ ((~x) & z));
  }

  function Maj (x, y, z) {
    return ((x & y) ^ (x & z) ^ (y & z));
  }

  Sha512.prototype._update = function(M) {

    var W = this._w
    var a, b, c, d, e, f, g, h
    var al, bl, cl, dl, el, fl, gl, hl

    a = this._a | 0
    b = this._b | 0
    c = this._c | 0
    d = this._d | 0
    e = this._e | 0
    f = this._f | 0
    g = this._g | 0
    h = this._h | 0

    al = this._al | 0
    bl = this._bl | 0
    cl = this._cl | 0
    dl = this._dl | 0
    el = this._el | 0
    fl = this._fl | 0
    gl = this._gl | 0
    hl = this._hl | 0

    for (var i = 0; i < 80; i++) {
      var j = i * 2

      var Wi, Wil

      if (i < 16) {
        Wi = W[j] = M.readInt32BE(j * 4)
        Wil = W[j + 1] = M.readInt32BE(j * 4 + 4)

      } else {
        var x  = W[j - 15*2]
        var xl = W[j - 15*2 + 1]
        var gamma0  = S(x, xl, 1) ^ S(x, xl, 8) ^ (x >>> 7)
        var gamma0l = S(xl, x, 1) ^ S(xl, x, 8) ^ S(xl, x, 7)

        x  = W[j - 2*2]
        xl = W[j - 2*2 + 1]
        var gamma1  = S(x, xl, 19) ^ S(xl, x, 29) ^ (x >>> 6)
        var gamma1l = S(xl, x, 19) ^ S(x, xl, 29) ^ S(xl, x, 6)

        // W[i] = gamma0 + W[i - 7] + gamma1 + W[i - 16]
        var Wi7  = W[j - 7*2]
        var Wi7l = W[j - 7*2 + 1]

        var Wi16  = W[j - 16*2]
        var Wi16l = W[j - 16*2 + 1]

        Wil = gamma0l + Wi7l
        Wi  = gamma0  + Wi7 + ((Wil >>> 0) < (gamma0l >>> 0) ? 1 : 0)
        Wil = Wil + gamma1l
        Wi  = Wi  + gamma1  + ((Wil >>> 0) < (gamma1l >>> 0) ? 1 : 0)
        Wil = Wil + Wi16l
        Wi  = Wi  + Wi16 + ((Wil >>> 0) < (Wi16l >>> 0) ? 1 : 0)

        W[j] = Wi
        W[j + 1] = Wil
      }

      var maj = Maj(a, b, c)
      var majl = Maj(al, bl, cl)

      var sigma0h = S(a, al, 28) ^ S(al, a, 2) ^ S(al, a, 7)
      var sigma0l = S(al, a, 28) ^ S(a, al, 2) ^ S(a, al, 7)
      var sigma1h = S(e, el, 14) ^ S(e, el, 18) ^ S(el, e, 9)
      var sigma1l = S(el, e, 14) ^ S(el, e, 18) ^ S(e, el, 9)

      // t1 = h + sigma1 + ch + K[i] + W[i]
      var Ki = K[j]
      var Kil = K[j + 1]

      var ch = Ch(e, f, g)
      var chl = Ch(el, fl, gl)

      var t1l = hl + sigma1l
      var t1 = h + sigma1h + ((t1l >>> 0) < (hl >>> 0) ? 1 : 0)
      t1l = t1l + chl
      t1 = t1 + ch + ((t1l >>> 0) < (chl >>> 0) ? 1 : 0)
      t1l = t1l + Kil
      t1 = t1 + Ki + ((t1l >>> 0) < (Kil >>> 0) ? 1 : 0)
      t1l = t1l + Wil
      t1 = t1 + Wi + ((t1l >>> 0) < (Wil >>> 0) ? 1 : 0)

      // t2 = sigma0 + maj
      var t2l = sigma0l + majl
      var t2 = sigma0h + maj + ((t2l >>> 0) < (sigma0l >>> 0) ? 1 : 0)

      h  = g
      hl = gl
      g  = f
      gl = fl
      f  = e
      fl = el
      el = (dl + t1l) | 0
      e  = (d + t1 + ((el >>> 0) < (dl >>> 0) ? 1 : 0)) | 0
      d  = c
      dl = cl
      c  = b
      cl = bl
      b  = a
      bl = al
      al = (t1l + t2l) | 0
      a  = (t1 + t2 + ((al >>> 0) < (t1l >>> 0) ? 1 : 0)) | 0
    }

    this._al = (this._al + al) | 0
    this._bl = (this._bl + bl) | 0
    this._cl = (this._cl + cl) | 0
    this._dl = (this._dl + dl) | 0
    this._el = (this._el + el) | 0
    this._fl = (this._fl + fl) | 0
    this._gl = (this._gl + gl) | 0
    this._hl = (this._hl + hl) | 0

    this._a = (this._a + a + ((this._al >>> 0) < (al >>> 0) ? 1 : 0)) | 0
    this._b = (this._b + b + ((this._bl >>> 0) < (bl >>> 0) ? 1 : 0)) | 0
    this._c = (this._c + c + ((this._cl >>> 0) < (cl >>> 0) ? 1 : 0)) | 0
    this._d = (this._d + d + ((this._dl >>> 0) < (dl >>> 0) ? 1 : 0)) | 0
    this._e = (this._e + e + ((this._el >>> 0) < (el >>> 0) ? 1 : 0)) | 0
    this._f = (this._f + f + ((this._fl >>> 0) < (fl >>> 0) ? 1 : 0)) | 0
    this._g = (this._g + g + ((this._gl >>> 0) < (gl >>> 0) ? 1 : 0)) | 0
    this._h = (this._h + h + ((this._hl >>> 0) < (hl >>> 0) ? 1 : 0)) | 0
  }

  Sha512.prototype._hash = function () {
    var H = new Buffer(64)

    function writeInt64BE(h, l, offset) {
      H.writeInt32BE(h, offset)
      H.writeInt32BE(l, offset + 4)
    }

    writeInt64BE(this._a, this._al, 0)
    writeInt64BE(this._b, this._bl, 8)
    writeInt64BE(this._c, this._cl, 16)
    writeInt64BE(this._d, this._dl, 24)
    writeInt64BE(this._e, this._el, 32)
    writeInt64BE(this._f, this._fl, 40)
    writeInt64BE(this._g, this._gl, 48)
    writeInt64BE(this._h, this._hl, 56)

    return H
  }

  return Sha512

}
